Anger with the police was a key cause of the riots which hit England in August, a study has said.

Widespread frustration with policing methods, and a deeper sense of antipathy with the force as a whole, was widespread among the rioters according to the study by the London School of Economics and the Guardian.

Riots in cities across England including London, Manchester and Birmingham resulted in the most serious widespread public disorder for a generation in August.

Five people died during the disturbances, and more than 4,000 people have since been arrested for offences connected to the riots.

Opportunism was also a significant factor, the interviewed rioters claimed. There was a "perceived suspension of normal rules", the Guardian said, which presented a chance to simply obtain "free stuff" and luxury items.

Gangs were less of a factor than claimed by some including Prime Minister David Cameron during the riots, the study claims. It says that most gangs suspended their own rivalries for the duration of the riots, and said that many members played marginal roles.

The report also claims that social media networks including Facebook and Twitter were not a significant cause of the violence, but adds that BlackBerry Messenger was used "extensively" to co-ordinate plans in advance.

The research was funded by the Joseph Rowntree Foundation and Open Society Foundations, and involved a team of more than 60 academics and journalists working to interview participants and victims of the riots over three months.

The Association of Chief Police Officers said in a statement: "The disorder seen in August was unprecedented in its scale of violence and the way in which events escalated rapidly. It took people by surprise, not enough police officers were available initially and it eventually required 16,000 of them to restore order.

"Of course the way in which those events took place and were seen by others through the media had an impact on confidence in the police, and it is important that lessons are learned from all the different processes and reports investigating what happened.

“In a survey of 270 rioters, it would be quite odd if a high proportion did not cite the police as a factor in their behaviour. But August also showed the ability of our police to restore order using robust, common sense policing in the British way."